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GETOPT(1) FreeBSD General Commands Manual GETOPT(1)
NAMEgetopt -- parse command options
SYNOPSISargs=`getoptoptstring$*` ; errcode=$?; set -- $args
DESCRIPTION
The getopt utility is used to break up options in command lines for easy
parsing by shell procedures, and to check for legal options. Optstring
is a string of recognized option letters (see getopt(3)); if a letter is
followed by a colon, the option is expected to have an argument which may
or may not be separated from it by white space. The special option `--'
is used to delimit the end of the options. The getopt utility will place
`--' in the arguments at the end of the options, or recognize it if used
explicitly. The shell arguments ($1$2 ...) are reset so that each
option is preceded by a `-' and in its own shell argument; each option
argument is also in its own shell argument.
EXIT STATUS
The getopt utility prints an error message on the standard error output
and exits with status > 0 when it encounters an option letter not
included in optstring.
EXAMPLES
The following code fragment shows how one might process the arguments for
a command that can take the options -a and -b, and the option -o, which
requires an argument.
args=`getopt abo: $*`
# you should not use `getopt abo: "$@"` since that would parse
# the arguments differently from what the set command below does.
if [ $? -ne 0 ]; then
echo 'Usage: ...'
exit 2
fi
set -- $args
# You cannot use the set command with a backquoted getopt directly,
# since the exit code from getopt would be shadowed by those of set,
# which is zero by definition.
while true; do
case "$1" in
-a|-b)
echo "flag $1 set"; sflags="${1#-}$sflags"
shift
;;
-o)
echo "oarg is '$2'"; oarg="$2"
shift; shift
;;
--)
shift; break
;;
esac
done
echo "single-char flags: '$sflags'"
echo "oarg is '$oarg'"
This code will accept any of the following as equivalent:
cmd -aoarg file file
cmd -a -o arg file file
cmd -oarg -a file file
cmd -a -oarg -- file file
SEE ALSOgetopts(1), sh(1), getopt(3)HISTORY
Written by Henry Spencer, working from a Bell Labs manual page. Behavior
believed identical to the Bell version. Example changed in FreeBSD ver-
sion 3.2 and 4.0.
BUGS
Whatever getopt(3) has.
Arguments containing white space or embedded shell metacharacters gener-
ally will not survive intact; this looks easy to fix but is not. People
trying to fix getopt or the example in this manpage should check the his-
tory of this file in FreeBSD.
The error message for an invalid option is identified as coming from
getopt rather than from the shell procedure containing the invocation of
getopt; this again is hard to fix.
The precise best way to use the set command to set the arguments without
disrupting the value(s) of shell options varies from one shell version to
another.
Each shellscript has to carry complex code to parse arguments halfway
correctly (like the example presented here). A better getopt-like tool
would move much of the complexity into the tool and keep the client shell
scripts simpler.
FreeBSD 10.2 January 26, 2011 FreeBSD 10.2